This section is intended to provide a background or context to the invention recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
Typical power shovels or excavators use a bucket or dipper assembly to scoop earth or other material from horizontal or vertical faces. These conventional power shovels have a fixed boom, and the dipper assembly is mounted on the boom via a crowd mechanism. The fixed boom extends upwardly and outwardly from the frame. The crowd mechanism includes two crowd sheaves and a saddle block on the boom, and half sheaves on both ends of the dipper handle. Two ropes are connected about the sheaves and are used to move the dipper handle translationally with respect to the saddle block. Once the dipper is filled with material, the dipper is moved to a deposit point to unload the material.
After the unloading sequence, the dipper often swings backwards, coming into contact with the boom and the crowd machinery, and causing damage to both. Conventional mining shovels have utilized bumpers (i.e., rubber pads or cushions) to protect the mining shovel from the impact of the dipper. These bumpers have generally been small devices mounted on the lower front end of the boom of the mining shovel. An example of such a bumper is found in U.S. Pat. No. 4,464,093 issued Aug. 7, 1984, for “Power Shovel Having Improed (sic) Hoist System.”
Conventional bumpers are generally adapted to engage the dipper when it is being retracted and to cushion the impact of its motion. Conventional bumpers may also be used to protect the crowd machinery from the mining environment, including bad weather and small impacts (i.e. rocks kicked up from a vehicle tire or debris spilling out of the dipper). However, conventional bumpers are often used to protect the boom structure, and may not fully protect the crowd machinery. For instance, conventional bumpers are typically not designed to prevent damage when the crowd machinery receives a heavy impact (i.e. impacts from dipper components, large boulders, or other mining trucks), or when the crowd machinery receives an impact at an uncommon angle.
Further, conventional bumpers are insufficient to protect the crowd machinery from dipper impacts in mining applications where blasting may be less successful, such as in some iron ore mines. In these types of applications, the dipper may be filled with large rocky materials, which can cause the dipper door to stick in the open position. When the dipper door is stuck in the open position and filled with rocky material, the dipper can strike the crowd mechanism with an inordinate amount of force or at an uncommon angle. Conventional bumpers are unable to more completely protect the crowd mechanism from these types of dipper impacts.